Conferences, Lectures, & Seminars
Events for February
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Nonlinear control and bioinspired underwater vehicle systems
Wed, Feb 13, 2008 @ 03:30 PM - 04:30 PM
Aerospace and Mechanical Engineering
Conferences, Lectures, & Seminars
Professor Kristi MorgansenUniversity of WashingtonDepartment of Aeronautics and AstronauticsUnderwater locomotion and propulsion for underwater vehicles provide rich applications for the development of control methods for nonlinear systems and underactuated mechanical systems. In the work here, the tasks of modeling and control for agile gait generation for robots built with fin propulsive and maneuvering surfaces are considered. Previous work for such bioinspired devices has shown that simplified models with quasistatic lift and drag can be used to construct trajectory tracking controls for forward and turning motions that strongly resemble biomimetic motions. Here we will evaluate the use of such models for agile maneuverability by comparing biomimetic fast start and snap turn data from experiment with simulation data from the model. Beyond single-vehicle applications, a number of current science applications indicate the need for operation of multivehicle groups composed of different types of vehicles operating in different media (air, water, space). Recent work in coordinated control of vehicle systems has shown that earlier studies in mathematics, physics, and chemistry with models of interconnected oscillators can be used to construct controls for coordinated vehicles. Additionally these oscillator models have been demonstrated to have direct connection to Frenet-Serret models of dynamics for nonholonomic systems (e.g. ground vehicles, fixed-wing aircraft, and underwater vehicles). The work presented here will address the construction of controls for oscilator-based analysis that allow a group of vehicles to track a moving target. Further, when these models are considered in a discrete time setting, effects of intermittent, dynamic and asynchronous communication can be incorporated into the dynamics. Stability bounds for particular group modes of behavior (identical heading or common point of rotation) can then be determined in the context of limited communication. Results are demonstrated in simulation and experiment with applications drawn from the engineering contexts of autonomous air and underwater vehicles as well as the biological context of schooling fish.Beyond single-vehicle applications, a number of current science applications indicate the need for operation of multivehicle groups composed of different types of vehicles operating in different media (air, water, space). Further, such systems are needed to operate with variable levels of autonomy and human interaction. Recent work in coordinated control of vehicle systems has shown that earlier studies in mathematics, physics, and chemistry with models of interconnected oscillators can be used to construct controls for coordinated vehicles. Additionally these oscillator models have been demonstrated to have direct connection to Frenet-Serret models of dynamics for nonholonomic systems (e.g. ground vehicles, fixed-wing aircraft, and underwater vehicles). The work presented here will address the construction of controls for oscillator-based analysis that allow a group of vehicles to track a moving target. Further, when these models are considered in a discrete time setting, effects of intermittent, dynamic and asynchronous communication can be incorporated into the dynamics. Stability bounds for particular group modes of behavior (identical heading or common point of rotation) can then be determined in the context of limited communication. Results are demonstrated in simulation and experiment with applications drawn from the engineering contexts of autonomous air and underwater vehicles as well as the biological context of schooling
fish.
Location: Seaver Science Library, Rm 150
Audiences: Everyone Is Invited
Contact: April Mundy
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Impact of sea-salt aerosol on the weekend effect
Wed, Feb 20, 2008 @ 03:30 PM - 04:30 PM
Aerospace and Mechanical Engineering
Conferences, Lectures, & Seminars
Donald DabdubProfessor of Mechanical and Aerospace EngineeringProfessor, Advanced Power and Energy ProgramUniversity of California, IrvineABSTRACT:The weekend effect has become an important issue in regulation as it may suggest that controlling NOx would be counter productive to reducing ozone concentrations. Current hypotheses suggest that the dynamics of NOx (changes of quantities and timing NOx emissions rates) explain in part the increase in ozone concentrations. In the past few years there have been new discoveries of atmospheric processes such as the chemistry of sea-salt aerosol in coastal areas. This study quantifies the impact that sea-salt aerosol has on air quality in urban regions. The focus area of this study is the South Coast Air Basin of California.
Particular emphasis will be placed to the impact of sea-salt aerosol to the weekend effect.Location: Seaver Science Library, Rm 150
Audiences: Everyone Is Invited
Contact: April Mundy
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Prospects for Very Large Space Telescopes: How Mass Scales with Structural Requirements
Wed, Feb 27, 2008 @ 03:30 PM - 04:30 PM
Aerospace and Mechanical Engineering
Conferences, Lectures, & Seminars
Lee Peterson ProfessorGary L. Roubos Endowed ChairDepartment Chair (on sabbatical)Director, Center for Aerospace StructuresDepartment of Aerospace Engineering SciencesUniversity of ColoradoBoulder, CO A conceptual design framework is presented for studying how the mass of a large space telescope mirror will depend on design disturbances, mirror diameter, and practical structural design constraints. A variety of on-orbit, launch, and ground test design requirements are considered, as are practical constraints on structural truss member properties. While prior work emphasized the trade between structural depth and overall mass fraction, this paper shows how these practical constraints limit the achievable structural depth, and thus define an optimal depth. An example of a tetrahedral support truss for a segmented mirror is presented. For lightly loaded design cases, it is observed that the minimum mass structure is determined by the simultaneous application of minimum allowable tube thickness, a specified strut Euler buckling load, and a specified strut pin-pin frequency. Closed form solutions are derived for the optimal structural depth and areal density. These are shown to be independent of the diameter of the telescope mirror.
Location: Seaver Science LIbrary, Rm 150
Audiences: Everyone Is Invited
Contact: April Mundy